Golf ball layer incorporating inhomogeneous materials

ABSTRACT

A golf ball of the present invention comprises a core of one or more layers and a cover of one or more layers surrounding the core. At least one of the core layers is comprised of a surface region. The surface region is a composite of cured core material and non-reactive particles. The non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer.

FIELD OF THE INVENTION

A golf ball of the present invention comprises a core of one or more layers and a cover of one or more layers surrounding the core. At least one of the core layers is comprised of a surface region. The surface region is a composite of cured core material and non-reactive particles. The non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into several general classes: (a) solid golf balls having one or more layers, and (b) wound golf balls. Solid golf balls include one-piece balls and multi-piece balls, one-piece balls are easy to construct and relatively inexpensive, but have poor playing characteristics and are thus generally limited for use as range balls. Two-piece balls are constructed with a generally solid core and a cover and are generally the most popular with recreational golfers because they are very durable and provide maximum distance.

Solid golf balls are typically made with a solid core encased by a cover, both of which can have multiple layers, such as a dual core having a solid center and an outer core layer, or a multi-layer cover having an inner and outer cover layer. Generally, golf ball cores and/or centers are constructed with a thermoset rubber, typically a polybutadiene-based composition. The cores are usually heated and crosslinked to create certain characteristics, such as higher or lower compression, which can impact the spin rate of the ball and/or provide better “feel.” These and other characteristics can be tailored to the needs of golfers of different abilities. From the perspective of a golf ball manufacturer, it is desirable to have cores exhibiting a wide range of properties, such as resilience, durability, spin, and “feel,” because this enables the manufacturer to make and sell many different types of golf balls suited to differing levels of ability.

Heretofore, most single core golf ball cores have had a conventional hard-to-soft hardness gradient from the surface of the core to the center of the core. The patent literature contains a number of references that discuss a hard surface to soft center hardness gradient across a golf ball core.

U.S. Pat. No. 4,650,193 to Molitor et al. generally discloses a hardness gradient in the surface layers of a core by surface treating a slug of curable elastomer with a cure-altering agent and subsequently molding the slug into a core having a hardness gradient.

U.S. Pat. No. 3,784,209 to Berman, et al. generally discloses a soft-to-hard hardness gradient. The '209 patent discloses a non-homogenous, molded golf ball with a core of “mixed” elastomers. A center sphere of uncured elastomeric material is surrounded by a compatible but different uncured elastomer. When both layers of elastomer are concurrently exposed to a curing agent, they become integral with one another, thereby forming a one-piece mixed core. The center of this core, having a higher concentration of the first elastomeric material, is harder than the outer layer.

Other patents discuss cores that receive a surface treatment to provide a soft ‘skin’. However, since the interior portions of these cores are untreated, they have the similar hard surface to soft center gradient as conventional cores. For example, U.S. Pat. No. 6,113,831 to Nesbitt et al. generally discloses a conventional core and a separate soft skin wrapped around the core. This soft skin is created by exposing the preform slug to steam during the molding process so that a maximum mold temperature exceeds a steam set point, and by controlling exothermic molding temperatures during molding. The skin comprises the radially-outermost 1/32 inch to ¼ inch of the spherical core. U.S. Pat. Nos. 5,976,443 and 5,733,206, both to Nesbitt et al., disclose the addition of water mist to the outside surface of the slug before molding in order to create a soft skin. The water allegedly softens the compression of the core by retarding crosslinking on the core surface, thereby creating an even softer soft skin around the hard central portion.

Conventional golf ball layers use homogenous compositions to provide hardness gradients. The conventional homogeneous compositions employ fillers which are uniform in a bulk sense. Any hardness gradients or color effects must therefore be achieved through the cure cycle.

There remains a need, however, to achieve a golf ball with one or more layers having different hardness gradients other than through the cure cycle.

BRIEF SUMMARY OF THE INVENTION

A golf ball of the present invention comprises a core of one or more layers and a cover of one or more layers surrounding the core. At least one of the core layers comprises a surface region. The surface region is a composite of cured core material and non-reactive particles. The non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer.

In one embodiment, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. In another embodiment, the core layer is a center having a diameter of less than 1.6 inches. Of course, other thickness and dimension of the core layers are contemplated and may be used in the in present invention.

In one embodiment, at least one of the core layers is comprised of a surface region. The surface region is a composite of cured core material and non-reactive particles. In one embodiment, the thickness of the surface region is less than half the thickness of the core layer. In another embodiment, the thickness of the surface region is less than 20 percent of the core layer thickness and greater than 5 percent of the core layer thickness. For example, in one embodiment, the surface region has a thickness of 0.005 to 0.025 inches.

The non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer. The size of non-reactive particles are less than 0.0083 inches, more preferably less than 0.0059 inches, and most preferably less than 0.0049 inches.

In one embodiment, the hardness of the surface region is harder than the hardness of the non-surface region of the outer core layer. In another embodiment the hardness of the surface region is softer than the hardness of the non-surface region of the outer core layer. In another embodiment, the hardness of the surface region is harder than the hardness of the non-surface region of the center. In yet another embodiment, the hardness of the surface region is softer than the hardness of the non-surface region of the center.

In one embodiment of a golf ball of the present invention, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. The outer core layer comprises a surface region which is a composite of composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of at least 30 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent in an amount of less than 20 pph of polybutadiene.

In another embodiment of a golf ball of the present invention, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. The outer core layer comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of at least 30 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance with ASTM Standard D1238, condition E.

In a further embodiment of a golf ball of the present invention, the core layer is a center having a diameter of less than 1.6 inches. The center comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of less than 25 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent in an amount of greater than 30 pph of polybutadiene.

In yet another embodiment, the core layer is a center having a diameter of less than 1.6 inches. The center comprises a surface region which is a composite of composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of less than 25 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance with ASTM Standard D1238, condition E.

In a method of forming a golf ball of the present invention comprises the following steps. First, non-reactive particles of a size less than 0.0083 inches are formed from a cured rubber composition or thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance with ASTM Standard D1238, condition E. Second, a prep of a rubber composition is formed comprising polybutadiene, a co-agent in the amount of less than 15 to 45 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, and a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. Third, the prep is coated with the non-reactive particles. Fourth, the prep is compression molded to form a golf ball core layer. Fifth, a cover is formed over the golf ball core layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are characteristic of the present invention are set forth in the appended claims. However, the preferred embodiments of the invention, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a two-piece golf ball having a cover and a core;

FIG. 2 is a cross-sectional view of a golf ball having a center, a core outer layer, and a cover; and

FIG. 3 is a cross-sectional view of a golf ball having a center, a core outer layer, and a cover having an inner and outer cover layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A golf ball of the present invention comprises a core of one or more layers and a cover of one or more layers surrounding the core. At least one of the core layers is comprised of a surface region. The surface region is a composite of cured core material and non-reactive particles. The non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer. The present invention is directed to a golf ball incorporating inhomogeneous materials to provide a range of different gradients, colors, or both within one or more layers.

In one embodiment, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. In another embodiment, the core layer is a center having a diameter of less than 1.6 inches. Of course, other thickness and dimension of the core layers are contemplated and may be used in the present invention.

The one or more layers of the golf ball may comprise a surface region disposed about one or more portions of the golf ball. In another embodiment, the golf ball comprises a core and a cover, and one or more layers of the core comprise the surface region. In a further embodiment, the golf ball comprises a core and a cover, and the cover comprises the surface region. Of course, it is contemplated that the surface region may be disposed anywhere within or about one or more surfaces of the golf ball including both the core and the cover.

In the surface region, the frequency of the cured core material and/or non-reactive particles is greater than the frequency of the cured core material and/or non-reactive particles in the bulk composition of the layer. Thus, the surface region will have higher localized amounts of cured core material and/or non-reactive particles to achieve desired properties for the surface region as discussed in more detail below. For example, it will be appreciated that golf ball cores may have cured core material and/or non-reactive particles in amounts from 0 to about 50 parts per 100. The corresponding surface region would have cured core material and/or non-reactive particles in amounts greater than the non-surface region of the core.

The surface region is a composite of cured core material and non-reactive particles. In one embodiment, the thickness of the surface region is less than half the thickness of the core layer. In another embodiment, the thickness of the surface region is less than 20 percent of the core layer thickness and greater than 5 percent of the core layer thickness. For example, in one embodiment, the surface region has a thickness of 0.005 to 0.025 inches.

In one embodiment, the non-reactive particles are comprised of ground cured-rubber or ground thermoplastic polymer. The non-reactive particles may also comprise a material selected from a group consisting of: active filler, inert filler, filler, polymer, ground polymer, ground polymer coating, regrind, reground rubber, pre-crosslinked material and mixtures thereof. The non-reactive particles provide a difference in gradients and therefore may incorporate other materials which provide similar effects. Of course, the materials used in the filler may include other materials known in the art such as ZnO or barium sulfate.

The non-reactive particles are disposed about one or more surfaces of the golf ball to provide a range of gradients within one or more layers of the golf ball. The non-reactive particles do not change their properties regardless of size. In addition, the non-reactive particles may be soaked, dipped, sprayed or otherwise contacted with a co-agent to effect the softness or hardness of the golf ball. For example, the non-reactive particles may be soaked in a plasticizer or peroxide depending upon the desired effect. The non-reactive particles can be soaked in a plasticizer to soften the particle, or peroxide and perhaps a co-agent to make the particles harder and then be cured. It will be appreciated that when the non-reactive particles are used as a carrier for these other materials, it will still then be cured and hardened for a second cross-linking.

One of the significant benefits of the non-reactive particles is to provide a gradient for an abrupt or non-smooth gradient transition in the golf ball. In one embodiment, the abrupt or non-smooth gradient transition occurs from steep gradients to shallow gradients. The abrupt or non-smooth gradient transition may occur from shallow gradients to steep gradients. The terms “shallow” and “steep” are defined by the slopes of the comparative plots of a property as a function of position away from the center of the core when the property is measured across the cross-section of a core. For example, a shallow hardness gradient is about −15 to about +15 Shore C, while a steeper hardness gradient is less than −15 Shore C or greater than +15 Shore C. This invention allows for abrupt or non-smooth property transitions, for example, in steep to shallow or shallow to steep, and variations thereof.

It will be appreciated that the non-reactive particles could be applied to any surface of a core (inner or outer or anywhere in between). In another embodiment, the hardness gradient may range from about 0 to 8 in JIS C Scale.

For example, the normal or regular core composition could be very hard but the non-reactive particles could be very soft. Alternatively, the normal or regular core composition could be very soft but the non-reactive particles could be very hard. Of course, the non-reactive particles could be disposed on any surface within the golf ball from the center to the outer surface of the golf ball. By manipulating the gradient using the non-reactive particles, the golf ball can be customized for the feel and spin.

The non-reactive particles may form additional regions within a layer of the golf ball. For example, the core may compromise one or more layers which have additional regions formed from the non-reactive particles with differing hardness gradients and color effects within the layer. The non-reactive particles may be added in different or varying amounts or different types and combinations, allowing for a non-uniform gradient to be formed inside a layer. By incorporating regions of non-reactive particles or material, the normal cure of the golf ball layer is altered by delaying the progress of the exotherm as it progresses toward the inner portion of the layer, thereby further altering the cure gradient. The non-reactive particles used may come from a different batch than the core and therefore can have a steeper or shallower gradient depending upon desired characteristics.

Depending on the non-reactive particles or material employed within the golf ball, the surface or gradient properties of the treated portion of the golf ball will be different from the bulk of the pre-form. By employing the non-reactive particles or material in the pre-form or sheet, it will allow gradients to be formed internally as well as modification of the surface properties depending upon desired hardness or softness.

In one embodiment, the size of non-reactive particles are less than 0.0083 inches, more preferably less than 0.0059 inches, and most preferably less than 0.0049 inches.

Generally, the cured core material is comprised of a base rubber, a co-agent, a filler, and a peroxide initiator. Suitable base rubbers include natural and synthetic rubbers including, but not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), styrene-butadiene rubber, styrenic block copolymer rubbers (such as SI, SIS, SB, SBS, SIBS, SEBS and the like, where “S” is styrene, “I” is isobutylene,“B” is butadiene, and “E” is for ethylene), butyl rubber, halobutyl rubber and mixtures thereof. Particularly preferred polybutadienes include high-cis neodymium-catalyzed polybutadienes and cobalt-, nickel-, or lithium-catalyzed polybutadienes. Suitable examples of commercially available polybutadienes include, but are not limited to, Buna CB high-cis neodymium-catalyzed polybutadiene rubbers, such as Buna CB 23 and Buna CB 22, and Buna CB high-cis cobalt-catalyzed polybutadiene rubbers, such as Buna CB 1220 and 1221, commercially available from Lanxess Corporation; SE BR-1220, commercially available from The Dow Chemical Company; Europrene® NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa®; UBEPOL-BR® rubbers, commercially available from UBE Industries, Inc.; BR 01, commercially available from Japan Synthetic Rubber Co., Ltd.; and Neodene high-cis neodymium-catalyzed polybutadiene rubbers, such as Neodene BR 40, commercially available from Karbochem.

Co-agents are commonly used with peroxides to increase the state of cure. Suitable co-agents include, but are not limited to, metal salts of unsaturated carboxylic acids; unsaturated vinyl compounds and polyfunctional monomers (e.g., trimethylolpropane trimethacrylate); phenylene bismaleimide; and combinations thereof. Particular examples of suitable metal salts include, but are not limited to, one or more metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates, wherein the metal is selected from magnesium, calcium, zinc, aluminum, lithium, nickel, and sodium. In a particular embodiment, the coagent is selected from zinc salts of acrylates, diacrylates, methacrylates, dimethacrylates, and mixtures thereof. In another particular embodiment, the coagent is zinc diacrylate (ZDA). When the coagent is zinc diacrylate and/or zinc dimethacrylate, the coagent is typically included in the crosslinked particle composition in an amount within the range having a lower limit of 0 or 5 or 10 or 15 or 20 or 25 parts by weight per 100 parts of the base polymer, and an upper limit of 25 or 30 or 35 or 40 or 45 or 50 or 75 or 100 parts by weight per 100 parts of the base polymer.

Exemplary fillers include precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, zinc sulfate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, carbonates (e.g., calcium carbonate, zinc carbonate, barium carbonate, and magnesium carbonate), metals (e.g., titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin), metal alloys (e.g., steel, brass, bronze, boron carbide whiskers, and tungsten carbide whiskers), oxides (e.g., zinc oxide, tin oxide, iron oxide, calcium oxide, aluminum oxide, titanium dioxide, magnesium oxide, and zirconium oxide), particulate carbonaceous materials (e.g., graphite, carbon black, cotton flock, natural bitumen, cellulose flock, and leather fiber), microballoons (e.g., glass and ceramic), fly ash, core material that is ground and recycled, nanofillers and combinations thereof.

Peroxide initiator agents are generally present in the rubber base in an amount of at least 0.05 parts by weight per 100 parts of the base rubber, or an amount within the range having a lower limit of 0.05 parts or 0.1 parts or 0.25 parts or 0.5 parts or 0.75 parts or 1 part or 1.5 parts by weight per 100 parts of the base rubber, and an upper limit of 2.5 parts or 3 parts or 5 parts or 10 parts by weight per 100 parts of the base rubber.

Golf balls of the present invention may have a variety of constructions with the non-reactive particles or material disposed in a variety of these configurations. The golf balls can include one-piece, two-piece, multi-layer, and wound golf balls having a variety of core structures, intermediate layers, covers, and coatings. Golf ball cores may comprise a single, unitary layer, comprising the entire core from the center of the core to its outer periphery. Alternatively, the cores may comprise or consist of a center surrounded by at least one outer core layer. The center, innermost portion of such multi-layer cores is most often solid, but may be hollow or liquid-, gel-, or gas-filled. The outer core layer may be solid, or it may be a wound layer formed of a tensioned elastomeric or non-elastomeric material. Golf ball covers may also include one or more layers, such as a double cover having an inner and outer cover layer. Optionally, additional intermediate layers may be disposed between the core and cover. In one embodiment of the present invention, golf ball includes a core and a cover layer. In another embodiment, the golf ball includes a core, an intermediate layer, and a cover layer.

The core is enclosed with a cover, which may be a single-, dual-, or multi-layer cover. In a particular embodiment, the cover has an overall thickness of 0.010 or 0.020 or 0.025 or 0.030 or 0.040 or 0.045 or 0.050 or 0.060 or 0.070 or 0.075 or 0.080 or 0.090 or 0.100 or 0.150 or 0.200 or 0.300 or 0.500 inches, or an overall thickness within a range having a lower limit and an upper limit selected from these values.

Suitable cover materials include, but are not limited to, ionomer resins and blends thereof (e.g., Surlyn® ionomer resins and DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, all of which are commercially available from E. I. du Pont de Nemours and Company; lotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylic acid copolymers, commercially available from The Dow Chemical Company; and Clarix® ionomer resins, commercially available from A. Schulman Inc.); polyurethanes; polyureas; copolymers and hybrids of polyurethane and polyurea; polyethylene, including, for example, low density polyethylene, linear low density polyethylene, and high density polyethylene; polypropylene; rubber-toughened olefin polymers; acid copolymers, e.g., (meth)acrylic acid, which do not become part of an ionomeric copolymer; plastomers; flexomers; styrene/butadiene/styrene block copolymers; styrene/ethylene-butylene/styrene block copolymers; dynamically vulcanized elastomers; ethylene vinyl acetates; ethylene methyl acrylates; polyvinyl chloride resins; polyamides, amide-ester elastomers, and graft copolymers of ionomer and polyamide, including, for example, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc; crosslinked trans-polyisoprene and blends thereof; polyester-based thermoplastic elastomers, such as Hytrel®, commercially available from E. I. du Pont de Nemours and Company; polyurethane-based thermoplastic elastomers, such as Elastollan®, commercially available from BASF; synthetic or natural vulcanized rubber; and combinations thereof.

Compositions comprising an ionomer or a blend of two or more ionomers are particularly suitable cover materials. Preferred ionomeric cover compositions include:

-   -   (a) a composition comprising a “high acid ionomer” (i.e., having         an acid content of greater than 16 wt %), such as Surlyn® 8150         ionomer resin;     -   (b) a composition comprising a high acid ionomer and a maleic         anhydride-grafted non-ionomeric polymer (e.g., Fusabond®         functionalized polymers). A particularly preferred blend of high         acid ionomer and maleic anhydride-grafted polymer is a 84 wt         %/16 wt % blend of Surlyn® 8150 ionomer resin and Fusabond®.         Blends of high acid ionomers with maleic anhydride-grafted         polymers are further disclosed, for example, in U.S. Pat. Nos.         6,992,135 and 6,677,401, the entire disclosures of which are         hereby incorporated herein by reference;     -   (c) a composition comprising a 50/45/5 blend of Surlyn® 8940         ionomer resin/Surlyn® 9650 ionomer resin/Nucrel® 960 acid         copolymer resin, preferably having a material hardness of from         80 to 85 Shore C;     -   (d) a composition comprising a 50/25/25 blend of Surlyn® 8940         ionomer resin/Surlyn® 9650 ionomer resin /Surlyn® 9910 ionomer         resin, preferably having a material hardness of about 90 Shore         C;     -   (e) a composition comprising a 50/50 blend of Surlyn® 8940         ionomer resin/Surlyn® 9650 ionomer resin, preferably having a         material hardness of about 86 Shore C;     -   (f) a composition comprising a blend of Surlyn® 7940 ionomer         resin/Surlyn® 8940 ionomer resin, optionally including a melt         flow modifier;     -   (g) a composition comprising a blend of a first high acid         ionomer and a second high acid ionomer, wherein the first high         acid ionomer is neutralized with a different cation than the         second high acid ionomer (e.g., 50/50 blend of Surlyn® 8150         ionomer resin and Surlyn® 9150 ionomer resin), optionally         including one or more melt flow modifiers such as an ionomer,         ethylene-acid copolymer or ester terpolymer; and     -   (h) a composition comprising a blend of a first high acid         ionomer and a second high acid ionomer, wherein the first high         acid ionomer is neutralized with a different cation than the         second high acid ionomer, and from 0 to 10 wt % of an         ethylene/acid/ester ionomer wherein the ethylene/acid/ester         ionomer is neutralized with the same cation as either the first         high acid ionomer or the second high acid ionomer or a different         cation than the first and second high acid ionomers (e.g., a         blend of 40-50 wt % Surlyn® 8140 ionomer resin, 40-50 wt %         Surlyn® 9120 ionomer resin, and 0-10 wt % Surlyn® 6320 ionomer         resin).

Surlyn® 8150 ionomer resin, Surlyn® 8940 ionomer resin, and Surlyn® 8140 ionomer resin are different grades of E/MAA copolymer in which the acid groups have been partially neutralized with sodium ions. Surlyn® 9650 ionomer resin, Surlyn® 9910 ionomer resin, Surlyn® 9150 ionomer resin, and Surlyn® 9120 ionomer resin are different grades of E/MAA copolymer in which the acid groups have been partially neutralized with zinc ions. Surlyn® 7940 ionomer resin is an E/MAA copolymer in which the acid groups have been partially neutralized with lithium ions. Surlyn® 6320 ionomer resin is a very low modulus magnesium ionomer with a medium acid content. Nucrel® 960 acid copolymer resin is an E/MAA copolymer resin nominally made with 15 wt % methacrylic acid. Surlyn® ionomers, Fusabond® polymers, and Nucrel® copolymers are commercially available from E. I. du Pont de Nemours and Company.

Ionomeric cover compositions can be blended with non-ionic thermoplastic resins, particularly to manipulate product properties. Examples of suitable non-ionic thermoplastic resins include, but are not limited to, polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea, thermoplastic polyether block amides (e.g., Pebax® block copolymers, commercially available from Arkema Inc.), styrene-butadiene-styrene block copolymers, styrene(ethylene-butylene)-styrene block copolymers, polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene-(meth)acrylate, polyethylene-(meth)acrylic acid, functionalized polymers with maleic anhydride grafting, Fusabond® functionalized polymers commercially available from E. I. du Pont de Nemours and Company, functionalized polymers with epoxidation, elastomers (e.g., ethylene propylene diene monomer rubber, metallocene-catalyzed polyolefin) and ground powders of thermoset elastomers.

Suitable ionomeric cover materials are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated by reference.

Ionomer golf ball cover compositions may include a flow modifier, such as, but not limited to, Nucrel® acid copolymer resins, and particularly Nucrel® 960 acid copolymer resin. Nucrel® acid copolymer resins are commercially available from E. I. du Pont de Nemours and Company.

Polyurethanes, polyureas, and blends and hybrids of polyurethane/polyurea are also particularly suitable for forming cover layers. Suitable polyurethanes are further disclosed, for example, in U.S. Pat. Nos. 5,334,673, 6,506,851, 6,756,436, 6,867,279, 6,960,630, and 7,105,623, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyureas are further disclosed, for example, in U.S. Patent Nos. 5,484,870 and 6,835,794, and U.S. Patent Application No. 60/401,047, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyurethane-urea cover materials include polyurethane/polyurea blends and copolymers comprising urethane and urea segments, as disclosed in U.S. Patent Application Publication No. 2007/0117923, the entire disclosure of which is hereby incorporated herein by reference.

Suitable cover materials and constructions also include, but are not limited to, those disclosed in U.S. Patent Application Publication No. 2005/0164810, U.S. Pat. Nos. 5,919,100, 6,117,025, 6,767,940, and 6,960,630, and PCT Publications WO00/23519 and WO00/29129, the entire disclosures of which are hereby incorporated herein by reference.

In a particular embodiment, the cover is a single layer, preferably formed form a composition selected ionomer compositions, polyurethanes, polyureas, and blends and hybrids of polyurethane/polyurea. The single layer cover preferably has an outer surface hardness of 65 Shore D or less, or 60 Shore D or less, or 45 Shore D or less, or 40 Shore D or less, or an outer surface hardness of 25 Shore D or 30 Shore D or 35 Shore D or 40 Shore D, or an outer surface hardness within a range having a lower limit and an upper limit selected from these values.

In another particular embodiment, the cover is a dual- or multi-layer cover comprising an inner cover layer, an outer cover layer, and optionally one or more intermediate cover layers. In a particular aspect of this embodiment, the inner cover layer or optional intermediate cover layer is formed from an ionomer composition and the outer cover layer is formed from a polyurethane or polyurea composition.

The golf ball cover composition of the present invention can also include one or more other additives as desired in order to produce a golf ball with specific characteristics or properties. Suitable additives include, but are not limited to, chemical blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nano-fillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, TiO₂, acid copolymer wax, surfactants, and fillers, such as zinc oxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc carbonate, barium carbonate, clay, tungsten, tungsten carbide, silica, lead silicate, regrind (recycled material), and mixtures thereof. Suitable additives are more fully described in, for example, U.S. Pat. No. 7,041,721, the entire disclosure of which is hereby incorporated herein by reference. Other optional additives can include fibers, flakes, particulates, microspheres, pre-expanded beads of glass, ceramic, metal or polymer, and the like which may be optionally foamed. Depending on the additive, such additives can be present in an amount of from 0.01 wt % to 60 wt %, based on the total weight of the composition.

Referring to FIG. 1, a golf ball 10 of another embodiment comprises a core 12 having a single core layer and a cover 16 surrounding the core 12. The single core layer is comprised of a surface region 38. The surface region 38 is a composite of cured core material and non-reactive particles. The cured core material is comprised of a base rubber comprising polybutadiene, a co-agent comprising ZDA in the amount of at least 25 parts per hundred (“pph”) of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, and a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent comprising ZDA in an amount of less than 20 pph of polybutadiene to provide a softer outer surface.

Referring to FIG. 2, a golf ball 20 of another embodiment comprises a core having a center 22 and a core outer layer 24, and a cover 26 surrounding the core. The core is comprised of a surface region 38 located between the center 22 and the core outer layer 24. The surface region 38 is a composite of cured core material and non-reactive particles. The cured core material is comprised of a base rubber comprising polybutadiene, a co-agent comprising ZDA in the amount of at least 25 parts per hundred (“pph”) of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, and a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent comprising ZDA in an amount of less than 20 pph of polybutadiene to provide a softer outer surface.

Referring to FIG. 3, a golf ball 30 of another embodiment comprising a core having a center 32 and a core outer layer 34; and a cover comprising an inner cover layer 37 and outer cover layer 36 surrounding the core. The core outer layer is comprised of a surface region 38. The surface region 38 is a composite of cured core material and non-reactive particles. The center 32 comprises polybutadiene, ZDA in the amount of at least 20 pph of the polybutadiene, a density adjusting filler, and a peroxide initiator. The cured core material of the core outer layer 34 comprises polybutadiene, ZDA in the amount of at least 30 pph of the polybutadiene to provide a harder, more resilient core. The non-reactive particles in the core outer layer 34 are formed from ground center material, wherein the ground center material comprises polybutadiene and co-agent comprising ZDA in an amount of less than 20 pph of polybutadiene to provide a softer outer surface. In this embodiment, the center has a very steep gradient and abrupt or non-smooth transition to a core outer layer having a very shallow gradient having the non-reactive particles.

In an alternative embodiment of FIG. 3, the non-reactive particles in the core outer layer 34 of FIG. 3 are formed from DuPont's Hytrel® 3078 to provide a softer outer surface.

In another alternative embodiment of FIG. 3, the non-reactive particles are provided in the center 32 to provide a very shallow gradient and abrupt or non-smooth transition to a core outer layer having a very steep gradient.

In one embodiment of a golf ball of the present invention, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. The outer core layer comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of a base rubber comprising polybutadiene, a co-agent in the amount of at least 30 parts per hundred (“pph”) of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent in an amount of less than 20 pph of polybutadiene.

In another embodiment of a golf ball of the present invention, the core layer is an outer core layer having a thickness of 0.03 to 0.5 inches. The outer core layer comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of at least 30 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance to ASTM Standard D1238, condition E, using a Tinius Olsen Extrusion Plastometer. The quantity of melt flow is measured by placing the sample in a heated barrel where it is held for a certain time then forced through a die using a weighted piston. The ASTM standard specifies the barrel and die dimensions and suggests a number of temperature and weight conditions typically chosen to give results between 0.15 and 50 g/10 min. Melt flow results are reported as grams of material extruded over a 10-minute timer interval at a specified temperature and load. The 190° C./2.16 kg condition is an industry standard used to report the melt flow for golf ball applications.

In a further embodiment of a golf ball of the present invention, the core layer is a center having a thickness of less than 1.6 inches. The center comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of less than 25 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground cured-rubber, wherein the ground cured-rubber is comprised of polybutadiene and co-agent in an amount of greater than 30 pph of polybutadiene.

In yet another embodiment, the core layer is a center having a diameter of less than 1.6 inches. The center comprises a surface region which is a composite of cured core material and non-reactive particles. The cured core material is comprised of polybutadiene, a co-agent in the amount of less than 25 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. The non-reactive particles are formed from ground thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance to ASTM Standard D1238, condition E.

In one embodiment, a method of forming a golf ball of the present invention comprises the following steps. First, non-reactive particles of less than 0.0083 inches are formed from a cured rubber composition or thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance to ASTM Standard D1238, condition E. Second, a prep of a rubber composition is formed comprising polybutadiene, a co-agent in the amount of less than 15 to 45 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, and a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene.

Third, the prep is coated, sprinkled, or rolled with the non-reactive particles to provide a steep or shallow gradient depending upon the type and quantity of the non-reactive particles. One or more surfaces of the prep is covered with the non-reactive particles or material to provide gradient differences. A pre-formed prep may be modified internally, on its surface, or both by adding the non-reactive particles. By treating an outer surface of the prep, the non-reactive particles are used to impart gradient properties to the outer surface of the prep that are different (i.g. steep or shallow than) the properties of the cured core material. Fourth, the prep is compression molded to form a golf ball core layer. Fifth, a cover is formed over the golf ball core layer.

In another embodiment, a method of forming a golf ball of the present invention comprises the following steps. First, non-reactive particles of less than 0.0083 inches are formed from a cured rubber composition or thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance to ASTM Standard D1238, condition E. Second, a pair of half-shells is formed from a rubber composition comprising polybutadiene, a co-agent in the amount of less than 15 to 45 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, and a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. Third, an inner surface of the half-shells is coated with the non-reactive particles. It is also contemplated that the non-reactive particles may also be provided on the outer surface of the half-shells or both on the inner and outer surface. Fourth, the half-shells are compression molded around a center to form a golf ball core layer with a composite inner surface. Fourth, a cover is formed over the golf ball core layer.

In yet another embodiment, a method of forming a golf ball of the present invention comprises the following steps. First, non-reactive particles of less than 0.0083 inches are formed from a cured rubber composition or thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C. using a 2.16 kg weight in accordance to ASTM Standard D1238, condition E. Second, a sheet of a rubber composition is formed comprising polybutadiene, a co-agent in the amount of less than 15 to 45 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene. Third, the sheet is coated with the non-reactive particles. Of course, other methods for applying the non-reactive particles to the prep or sheet may be employed known in the art. Fourth, the sheet is rolled to form a cylinder of material and cutting the cylinder into preps. Fifth, the preps are compression molded to form golf ball core layers. Sixth, a cover is formed over the golf ball core layers.

The present multilayer golf ball can have an overall diameter of any size. Although the United States Golf Association (“USGA”) specifications limit the minimum size of a competition golf ball to 1.680 inches. There is no specification as to the maximum diameter. Golf balls of any size, however, can be used for recreational play. The preferred diameter of the present golf balls is from about 1.680 inches to about 1.800 inches. The more preferred diameter is from about 1.680 inches to about 1.760 inches. The most preferred diameter is about 1.680 inches to about 1.740 inches.

The surface region of the present invention may also be used in golf equipment, in particular, inserts for golf clubs, such as putters, irons, and woods, and in golf shoes and components thereof.

Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials and others in the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.

While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objective stated above, it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments, which would come within the spirit and scope of the present invention. 

1. A golf ball, comprising: a core of one or more layers and a cover of one or more layers surrounding the core; wherein at least one of the core layers comprises a surface region which is a composite of cured core material and non-reactive particles comprised of ground cured-rubber or ground thermoplastic polymer.
 2. The golf ball of claim 1, wherein the core layer comprises an outer core layer having a thickness of 0.03 to 0.5 inches.
 3. The golf ball of claim 1, wherein the core layer is a center having a diameter of less than 1.6 inches.
 4. The golf ball of claim 1, wherein the size of non-reactive particles are less than 0.0083 inches.
 5. The golf ball of claim 1, wherein the size of non-reactive particles are less than 0.0059 inches.
 6. The golf ball of claim 1, wherein the size of non-reactive particles are less than 0.0049 inches.
 7. The golf ball of claim 1, wherein a thickness of the surface region is less than half the a thickness of the core layer.
 8. The golf ball of claim 7, wherein the thickness of the surface region is between 5 and 20% of the thickness of the core layer.
 9. The golf ball of claim 1, wherein the surface region has a thickness of 0.005 to 0.025 inches.
 10. The golf ball of claim 2, wherein the hardness of the surface region is harder than the hardness of a non-surface region of the outer core layer.
 11. The golf ball of claim 2, wherein the hardness of the surface region is softer than the hardness of the a non-surface region of the outer core layer.
 12. The golf ball of claim 3, wherein the hardness of the surface region is harder than the hardness of a non-surface region of the center.
 13. The golf ball of claim 3, wherein the hardness of the surface region is softer than the hardness of a non-surface region of the center.
 14. A method of forming a golf ball comprising the steps of: forming non-reactive particles of less than 0.0083 inches from a cured rubber composition or thermoplastic polymer having a melt flow rate of less than 10 g/10 min at 190° C./2.16 kg; forming a prep of a rubber composition comprising polybutadiene, a co-agent in the amount of less than 15 to 45 pph of the polybutadiene, a density adjusting filler in the amount of 0 to 35 pph of the polybutadiene, a peroxide initiator in the amount of 0.05 to 5 pph of the polybutadiene; coating the prep with the non-reactive particles; compression molding the prep to form a golf ball core layer; and forming a cover over the golf ball core layer.
 15. The golf ball of claim 1, wherein the core layer having the surface region comprises an inner region radially inward from the surface region in which the inner region is free of the non-reactive particles.
 16. The golf ball of claim 1, wherein the core layer having the surface region is formed by coating a prep with the non-reactive particles and compression molding the prep to form the core layer with the surface and inner regions. 